1. Field of the Invention
The present invention relates to a development device for use in image forming apparatuses such as copiers, printers, and facsimile machines that employ an electro-photographic process, and in particular to a development device that uses a single-component developer, and an image forming apparatus provided therewith.
2. Description of Related Art
Two types of development devices are known to be used in image forming apparatuses employing an electro-photographic process such as copiers, printers, facsimile machines, and multifunction peripherals having these functions; that is, a two-component development device that uses a developer containing a toner and a carrier, and a single-component development device that uses a developer containing only a toner but no carrier.
In a non-magnetic single-component development device, a toner stored in the device main body is fed to the surface of a development roller by a supply roller, and then a regulation member is pressed against this development roller to regulate the amount of toner and to triboelectrically charge the toner, and thereby a thin toner layer is formed. Then, the development roller is rotated so as to lead the toner to a development area that faces an image carrier to develop an electrostatic latent image formed on the image carrier. The toner remaining on the surface of the development roller is removed from the surface of the development roller by the supply roller, and fresh toner is supplied to the development roller. This system is advantageous in providing a low-cost image forming apparatus.
In non-magnetic development, a thin metal plate having elasticity (spring member) is typically used as a regulation member, which is flat-plate shaped in many cases. However, since the regulation member is designed to be pressed against a development roller with a slight pressure, the thin metal plate may, for example, become wavy (i.e., may warp) to degrade the flatness of the regulation member in its length direction (the direction of the length of the development roller). This inconveniently prevents the regulation member from being uniformly pressed against the development roller, causing uneven thickness of the thin toner layer, which results in uneven density of a formed image.
To solve the problem described above, for example, JP-A-H07-134485 and JP-A-H08-179624 disclose a development device where an elastic blade an end of which is bent in a direction opposite to a development roller is used as a regulation member. Also, JP-A-2004-125924 discloses a development unit having a detachable pressure dispersion member formed of a material such as urethane foam provided for dispersing pressure from the regulation member between the regulation member and the development roller.
However, with the method of JP-A-H07-134485 and JP-A-H08-179624, although it is possible to prevent the waving of the regulation member occurring near a portion thereof at which it is in contact with the development roller, since the regulation member needs to be bent at an end thereof, the contact between the regulation member and a seal member disposed to cover an end of the regulation member at the both ends of the development roller is weakened, and thus it is difficult to prevent the regulation member from warping along with maintaining the toner sealability of the development roller. The method is also inconvenient in that toner tends to be accumulated in the bent portion of the end of the regulation member. On the other hand, with the method of JP-A-2004-125924, although it is possible to prevent deformation of the regulation member attributable to factors such as the length of time from the shipping of a product until the user starts to use the product, shock and impact the product suffers during the time, and the temperature and humidity of the environment in which the product is placed during the time, the method gives no consideration to preventing deformation of the regulation member after the product starts to be used.